An Optical Phased Array (OPA) consists of multiple optical antennas, with each antenna emitting or accepting light of a particular amplitude and phase. The OPA can be used for a variety of purposes, such as a Light Detection and Ranging (LIDAR) apparatus. The OPA based LIDAR can exhibit flexible beam steering, beam forming, and multiple beam generation, which can be useful in a variety of applications, such as but not limited to autonomous vehicles. The OPA may be used as a transmitting beam-former, wherein the OPA is controlled such that the emissions form a desired far-field radiation pattern through interference.
OPAs can be realized using a photonic integrated circuit (PIC) platform (such as but not necessarily limited to a Silicon on Insulator (SOI) platform), in which the OPA components are formed on a substrate comprising optical waveguides. An example OPA of this type is described in “Sparse Aperiodic Arrays for Optical Beam Forming and LIDAR,” Komljenovic et al., Optics Express, Vol. 25, No. 3, February 2017, hereinafter referred to as Komljenovic, and in particular FIG. 1 of Komljenovic. However, the required optical components (including passive and active elements) in such a realization are often polarization dependent. For example, Komljenovic describes an OPA having a steering direction that depends upon an index of refraction, but uses SOI having silicon thickness of 220 nm to 500 nm and partially etched waveguides, which are well-known to persons skilled in the art to have a refractive index that depends strongly upon polarization. This means that for proper operation, the light provided to these components must be primarily of a particular polarization.
To address this issue, current OPAs typically receive input light which is preconfigured to the desired polarization prior to delivery to the PIC. For example, the input light can be generated away from the PIC platform with the desired polarization, and then transmitted to the PIC platform OPA input using a polarization maintaining (PM) fiber.
However, the use of polarization maintaining transmission media for connecting the OPA to the external polarization-controlled light source generally increases system cost and complexity. It would therefore be desirable to provide an OPA that is operable with a more generic light source, such as a generic fiber laser or another source of light with undefined polarization, wherein the undefined polarization may be static or may be time-varying.
Therefore there is a need for an OPA and associated method that obviates or mitigates one or more limitations of the prior art.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.